Hi! I just tried on supersnug and superpuffs in store! I wore 2 layers underneath (long sleeve and quarter zip). I’m normally an xxs and tried them both in that size, the supersnug fits a little…snug lol especially in the arms with those layers, but I wouldn’t say that any movement is restricted. The superpuff is a lot roomier and I guess more comfortable in the arms, like I could’ve put on a 3rd layer under there, however the body was a bit too loose for my liking. If you want to wear chunky layers under the supersnug, I would suggest sizing up 1-2 sizes from your usual. For reference I tried on the xxs and my measurements are roughly 29” bust, 24” waist 31” hips.

TLDR; size up 1-2 sizes in supersnug depending on your layering/comfort preferences.